1. Field
This disclosure relates to detecting and identifying targets using a radar system.
2. Description of the Related Art
Radar systems typically transmit an RF signal and receive a portion of the RF signal returned or reflected from targets and other objects. While radars may transmit a wide variety of signals, a common form of radar transmits a narrow beam of RF energy, typically within the microwave or millimeter wave portions of the electromagnetic spectrum. A target is typically detected by monitoring the amplitude of a return signal reflected or scattered from the target. Some radar systems determine the velocity of a target from the frequency difference between the transmitted RF signal and the return signal due to the Doppler effect. Other radar systems transmit a pulsed RF signal and determine the distance to a target from the elapsed time between a transmitted pulse and a returned pulse.
The return signal received from a typical target, such as a weapon or a vehicle, may differ substantially, in both the time domain and the frequency domain, from the transmitted RF signal. Some conventional radar systems attempt to recognize or identify the type of a target from the time-frequency characteristics of the returned pulses. A typical radar system with automatic target recognition converts the return signal to digital form and then extracts time-frequency information. For example, the frequency spectrum, as a function of time, of the returned pulses may be calculated using a windowed Fourier transform or other computational technique. The time-frequency characteristics of the return signal may then be matched with the time-frequency characteristics of a plurality of known objects. Numerical comparison, vector distance calculation, correlation, and/or other analytical techniques may be used to determine a degree of similarity between the extracted time-frequency information and the time-frequency characteristics of the known objects. A target may be considered to be identified if the degree of similarity with a known object exceeds a predetermined threshold. Such conventional automatic target recognition requires substantial and costly processing capability in the radar receiver.